Flexible circuit board and method for manufacturing same

ABSTRACT

A method for manufacturing a flexible circuit board includes providing a first laminated structure, the first laminated structure including two first wiring boards, a first adhesive layer sandwiched between the two first wiring boards, and a first conductive structure. The first conductive structure penetrates the two first wiring boards and the first adhesive layer and electrically connects the two first wiring boards. The first adhesive layer defines a first opening, the first opening includes a first edge away from the first conductive structure. The first laminated structure is cut along the first edge and then the two first wiring boards are unfolded. A flexible circuit board manufactured by such method is also disclosed.

FIELD

The subject matter herein generally relates to printed circuits,especially to a flexible circuit board and a method for manufacturingthe same.

BACKGROUND

Circuit boards are currently limited in length, a maximum length beingabout 620 mm. A circuit board with a length longer than 620 mm can bemade by soldering a plurality of circuit boards together, but a circuitboard made in this way will be of reduced quality due to inherentweaknesses in soldered joints and possibly poor soldering.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by wayof embodiment, with reference to the attached figures.

FIG. 1 is a cross-sectional view of two copper clad laminates and afirst adhesive layer, in accordance with an embodiment.

FIG. 2 is a cross-sectional view showing the two copper clad laminatesand the first adhesive layer shown in FIG. 1 pressed together.

FIG. 3 is a cross-sectional view showing a first conductive structureformed on one end of the structure shown in FIG. 2.

FIG. 4 is a cross-sectional view showing two first cover films pressedonto both sides of the structure shown in FIG. 3.

FIG. 5 is a cross-sectional view showing second copper clad laminatesand second adhesive layers provided on both sides of the structure shownin FIG. 4.

FIG. 6 is a cross-sectional view showing the structures of FIG. 5pressed together and pierced to a certain depth.

FIG. 7 is a cross-sectional view showing a second conductive structureformed on the structure shown in FIG. 6.

FIG. 8 is a cross-sectional view showing second cover films pressed ontoboth sides of the structure shown in FIG. 7.

FIG. 9 is a cross-sectional view of the structure shown in FIG. 0.8after cutting.

FIG. 10 is a cross-sectional view of a flexible circuit board when thestructure shown in FIG. 9 is unfolded.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures, and components havenot been described in detail so as not to obscure the related relevantfeature being described. Also, the description is not to be consideredas limiting the scope of the embodiments described herein.

The term “comprising,” when utilized, means “including, but notnecessarily limited to”; it specifically indicates open-ended inclusionor membership in the so-described combination, group, series, and thelike. When a first component is referred to as “connecting” to a secondcomponent, it is intended that the first component may be directlyconnected to the second component or may be indirectly connected to thesecond component via a third component between them.

A method for manufacturing a flexible circuit board in one embodimentincludes the following steps S1 to S4.

Referring to FIG. 4, at step S1, a first laminated structure 10 isprovided. The first laminated structure 10 includes two first wiringboards 12, a first adhesive layer 14, and a first conductive structure16. The first adhesive layer 14 is sandwiched between the first wiringboards 12. The first conductive structure 16 penetrates the first wiringboards 12 and the first adhesive layer 14, and electrically connects thefirst wiring boards 12.

Each of the first wiring boards 12 includes a first insulation layer 121and a first conductor layer 123 laminated on the first insulation layer121. A material of the first insulation layer 121 may be, but is notlimited to, polyimide, polyethylene terephthalate, or polyethylenenaphthalate. The material of the first conductor layer 123 may be, butis not limited to, a metal, such as copper, silver, or alloys thereof.In the embodiment, the material of the first insulation layer 121 ispolyimide, and the material of the first conductor layer 123 is copper.

The first insulation layer 121 is overlapped with and attached to thefirst adhesive layer 14. The first adhesive layer 14 defines a firstopening 141. Portions of the first wiring boards 12 are exposed in thefirst opening 141. The first opening 141 includes a first edge 143 awayfrom the first conductive structure 16 and a third edge 144 adjacent tothe first conductive structure 16.

The first conductive structure 16 electrically connects the firstconductor layers 123 of the first wiring boards 12. The first conductorlayer 123 includes a first end 1231 away from the first conductivestructure 16 and a second end 1232 adjacent to the first conductivestructure 16. Along a thickness direction H of the flexible circuitboard, a projection of the first end 1231 falls in a projection of thefirst opening 141.

According to one embodiment, the step S1 includes the following steps.

Referring to FIGS. 1 and 2, two first copper clad laminates 20 and thefirst adhesive layer 14 with the first opening 141 are provided, and thetwo first copper clad laminates 20 are pressed onto opposite sides ofthe first adhesive layer 14. Each of the first copper clad laminates 20includes the first insulation layer 121 and a first copper layer 21laminated on the first insulation layer 121.

Referring to FIG. 2, a first through hole 25 penetrating the firstcopper clad laminates 20 and the first adhesive layer 14 is defined. Thefirst through hole 25 does not communicate with the first opening 141.

Referring to FIG. 3, the first through hole 25 is electroplated to formthe first conductive structure 16 in the first through hole 25. In theembodiment, the first conductive structure 16 is a conductive via.

Referring to FIG. 4, each of the first copper layers is etched to formthe first conductor layer 123, thereby obtaining the first laminatedstructure 10.

The flexible circuit board further includes two first cover films 60.The first cover films 60 are pressed onto opposite sides of the firstlaminated structure 10 and cover the first conductor layers 123 of thefirst wiring boards 12. The first cover films 60 protect the firstconductor layers 23. The two first cover films 60 cover opposite ends ofthe first conductive structure 16. Each of the first cover films 60includes a first protective layer 61 and a first adhesive 63 coated onone side of the first protective layer 61, and the first adhesive 63infills the conductive via of the first laminated structure 10.

Referring to FIG. 8, at step S2, two second laminated structures 30 areformed on opposite sides of the first laminated structure 10. Each ofthe second laminated structures 30 includes a second wiring board 32, asecond adhesive layer 34 stacked on a side of the second wiring board32, and a second conductive structure 36. The second wiring board 32 isbonded to one first cover film 60 through the second adhesive layer 34.The second conductive structure 36 penetrates the second wiring board32, the second adhesive layer 34, and one first cover film 60, andelectrically connects the second wiring board 32 and one first wiringboard 12.

The second wiring board 32 includes a second insulation layer 321 and asecond conductor layer 323 stacked on the second insulation layer 321.The material of the second insulation layer 321 may be, but is notlimited to, polyimide, polyethylene terephthalate, or polyethylenenaphthalate. The material of the second conductor layer 323 may be, butis not limited to, a metal, such as copper, silver, or alloys thereof.In the embodiment, the material of the second insulation layer 321 ispolyimide, and the material of the second conductor layer 323 is copper.

The second insulation layer 321 is overlapped with and attached to thesecond adhesive layer 34. The second adhesive layer 34 defines a secondopening 341. A portion of the second wiring board 32 is exposed in thesecond opening 341. The second opening 341 includes a second edge 343away from the second conductive structure 36 and a fourth edge 344adjacent to the second conductive structure 36. The first conductivestructure 16 corresponds in position to the second opening 341.

The second conductive structure 36 corresponds in position to the firstopening 141. The second conductive structure 36 electrically connectsthe second conductor layer 323 and one first conductor layer 123. Thesecond conductor layer 323 includes a third end 3231 away from thesecond conductive structure 36 and a fourth end 3232 adjacent to thesecond conductive structure 36. Along the thickness direction H of theflexible circuit board, the projections of the third end 3231 and of thesecond end 1232 fall in a projection of the second opening 341. Alongthe thickness direction H of the flexible circuit board, a projection ofthe fourth end 3232 falls in the projection of the first opening 141.

According to one embodiment, the step S2 includes the following steps.

Referring to FIGS. 5 and 6, two second copper clad laminates 40 and twosecond adhesive layer 34 with second openings 341 are provided. Onesecond adhesive layer 34 and one second copper clad laminate 40 arepressed in said order onto one side of the first laminated structure 10,and another second adhesive layer 34 and another second copper cladlaminate 40 are pressed in said order onto the other side of the firstlaminated structure 10. Each of the second copper clad laminates 40includes the second insulation layer 321 and a second copper layer 41laminated on the second insulation layer 321.

Referring to FIG. 6, a second through hole 45 penetrating one secondcopper clad laminate 40, one second adhesive layer 34, and one firstcover film 60 is defined. A portion of one second conductor layer 323 isexposed from the second through hole 45. The second through hole 45corresponds in position to the first opening 141, and the second throughhole 45 does not communicate with the second opening 341.

Referring to FIG. 7, the second through hole 45 is electroplated to formthe second conductive structure 36 in the second through hole 45. In theembodiment, the second conductive structure 36 is a conductive via.

Referring to FIG. 8, each of the second copper layers of the secondcopper clad laminates is etched to form the second conductor layer 323,thereby obtaining two second laminated structures 30 formed on oppositesides of the first laminated structure 10.

The flexible circuit board further includes two second cover films 70.The second cover films 70 are pressed onto two sides of the two secondlaminated structures 30 away from the first laminated structure 10 andcover two second conductor layers 323 of the two second wiring boards32. The second cover films 70 protect the second conductor layers 323.Each of the second cover films 70 covers an end of one second conductivestructure 36 away from the first wiring board 12. Each of the secondcover films 70 defines a mask opening 74, and a portion of one secondconductor layer 323 is exposed from the mask opening 74. Each of thesecond cover films 70 includes a second protective layer 71 and a secondadhesive 73 coated on a side of the second protective layer 71. Thesecond adhesive 73 infills the conductive via of each of the secondlaminated structures 30.

Referring to FIGS. 9 and 10, at step S3, the first laminated structure10 and the two second laminated structures 30 are cut along the firstedge 143 and the second edge 343, and the two first wiring boards 12 andthe two second wiring boards 32 are unfolded to obtain the flexiblecircuit board 100. In the embodiment, after being unfolded, the twofirst wiring boards 12 and the two second wiring boards 32 are arrangedin a straight line in a length direction L of the flexible circuit board100.

After being unfolded, each of the first wiring boards 12 includes afirst bent portion 125, a first flat portion 126, and a second bentportion 127. The first bent portion 125 and the second bent portion 127are at an approximate right angle relative to the first flat portion126. In the embodiment, the first bent portion 125 and the second bentportion 127 extend in opposite directions from the ends of the firstflat portion 126. Two first bent portions 125 of the two first wiringboards 12 are electrically connected by the first conductive structure16 and are bonded together by the first adhesive layer 14 sandwichedtherebetween. The first conductive structure 16 penetrates the two firstbent portions 125.

After being unfolded, two second wiring boards 32 are connected to bothsides of the two first wiring boards 12, and each of the two secondwiring boards 32 includes a second flat portion 325 and a third bentportion 326. Relative to the second flat portion 325, the third bentportion 326 is approximately at a right angle. In the embodiment, thethird bent portion 326 extends from an end of the second flat portion325. The third bent portion 326 of each of the two second wiring boards32 is electrically connected to the second bent portion 127 of anadjacent first wiring board 12 by the second conductive structure 36.The third bent portion 326 adheres to the third bent portion 326 by thesecond adhesive layer 34 sandwiched therebetween. The second conductivestructure 36 penetrates the adjacent second and third bent portions 127,326.

In the method, a plurality of laminated structures are pressed together,followed by cutting along edges of the openings of the adhesive layersand unfolding, thereby increasing a length of a circuit board. In theflexible circuit board 100, the bent portions of adjacent wiring boardsare electrically connected by a conductive structure which penetratesthe wiring boards, so that the adjacent wiring boards are robustlyconnected in addition to being electrically connected.

While the present disclosure has been described with reference toparticular embodiments, the description is illustrative of thedisclosure and is not to be construed as limiting the disclosure.Therefore, those of ordinary skill in the art can make variousmodifications to the embodiments without departing from the scope of thedisclosure as defined by the appended claims.

1. A method for manufacturing a flexible circuit board comprising:providing a first laminated structure, the first laminated structurecomprising two first wiring boards, a first adhesive layer sandwichedbetween the two first wiring boards, and a first conductive structure,the first conductive structure penetrating the two first wiring boardsand the first adhesive layer and electrically connecting the two firstwiring boards, the first adhesive layer defining a first opening, thefirst opening comprising a first edge away from the first conductivestructure; cutting the first laminated structure along the first edge;and unfolding the two first wiring boards, thereby obtaining theflexible circuit board.
 2. The method of claim 1, further comprising:forming two second laminated structures on opposite sides of the firstlaminated structure, each of the two second laminated structurecomprising a second adhesive layer, a second wiring board stacked on aside of the second adhesive layer, and a second conductive structure,the second conductive structure penetrating the second wiring board andthe second adhesive layer and electrically connecting the second wiringboard and one of the two first wiring boards, the second conductivestructure corresponding in position to the first opening, the secondadhesive layer defining a second opening, the first conductive structurecorresponding in position to the second opening, the second openingcomprising a second edge away from the second conductive structure;cutting the two second laminated structures along the first edge andcutting the two second laminated structures and the first laminatedstructure along the second edge; and unfolding two wiring boards of thetwo second laminated structures.
 3. The method of claim 2, furthercomprising pressing two first cover films onto opposite sides of thefirst laminated structure, each of the two first cover films beingsandwiched between the first laminated structure and one of the twosecond laminated structures.
 4. The method of claim 3, wherein the firstconductive structure is a conductive via, each of the two first coverfilms comprises a first protective layer and a first adhesive coated ona side of the first protective layer, the first adhesive infilling theconductive via.
 5. The method of claim 2, further comprising pressingtwo second cover films onto two sides of the two second laminatedstructures away from the first laminated structure.
 6. The method ofclaim 2, wherein each of the two first wiring boards comprises a firstinsulation layer and a first conductor layer stacked on a side of thefirst insulation layer, the first conductor layer is electricallyconnected to the first conductive structure, the first conductor layercomprises a first end away from the first conductive structure and asecond end adjacent to the first adjacent structure; along a thicknessdirection of the flexible circuit board, a projection of the first endfalls in a projection of the first opening, and a projection of thesecond end falls in a projection of the second opening.
 7. The method ofclaim 6, wherein the second wiring board comprises a second insulationlayer and a second conductor layer stacked on a side of the secondinsulation layer, the second conductor layer is electrically connectedto the second conductive structure, the second conductor layer comprisesa third end away from the second conductive structure and a fourth endadjacent to the second conductive structure, along the thicknessdirection of the flexible circuit board, a projection of the third endfalls in the projection of the second opening, and a projection of thefourth end falls in the projection of the first opening.
 8. A flexiblecircuit board comprising: two wiring boards, each of the two wiringboards comprising a first bent portion, two first bent portions of thetwo wiring boards being connected to each other; a first adhesive layersandwiched between the two first bent portions; and a first conductivestructure penetrating the two first bent portions and the first adhesivelayer and electrically connecting the two first bent portions.
 9. Theflexible circuit board of claim 8, further comprising: two second wiringboards, each of the two second wiring boards comprises a third bentportion; and two second conductive structures; wherein each of the twofirst wiring boards further comprises a second bent portion, the secondbent portion adheres to the third bent portion by a second adhesivelayer sandwiched therebetween, each of the two second conductivestructures penetrates the second bent portion of each of the two firstwiring boards and the third bent portion of each of the two secondwiring boards.
 10. The flexible circuit board of claim 9, furthercomprising two first cover films covering the two first wiring boards,wherein the two first cover films cover opposite ends of the firstconductive structure.
 11. The flexible circuit board of claim 10,wherein each of the two first wiring boards comprises a first insulationlayer and a first conductor layer stacked on a side of the firstinsulation layer, the first conductor layer is electrically connected tothe first conductive structure and is covered by one of the two firstcover films.
 12. The flexible circuit board of claim 10, wherein thefirst conductive structure is a conductive via, each of the two firstcover films comprises a first protective layer and a first adhesivecoated on a side of the first protective layer, the first adhesiveinfilling the conductive via.
 13. The flexible circuit board of claim10, further comprising two second cover films covering the two secondwiring boards, an end of one of the two conductive structures penetratesone of the two first cover films, and the other end of the one of thetwo conductive structures is covered by one of the two second coverfilms.
 14. The flexible circuit board of claim 13, wherein each of thetwo second wiring boards comprises a second insulation layer and asecond conductor layer stacked on a side of the second insulation layer,the second conductor layer is covered one of the two second cover films.15. The flexible circuit board of claim 14, wherein each of the twosecond cover films defines a mask opening exposing a portion of thesecond conductor layer of each of the two second wiring boards.